An example creating a unit test in Rust. See the How to Write Tests section of the Rust book, and the Unit testing section of Rust by Example for additional details.

Unit Test

To write a text, prefix a function with the #[test] annotation. You can then use cargo test to run the test to confirm all the assertions are valid within that function.

fn main() {
    let sum = add( 3, 5 );
    println!("Sum: {}", sum);

fn add(a: i32, b: i32) -> i32 {
    a + b

fn test_add() {
    assert_eq!(add(1,2), 3);
    assert_eq!(add(-1,0), -1);
    assert_ne!(add(5, 6), 12); // not equal

An example result running cargo test

❯ cargo test
   Compiling tmp v0.1.0 (/home/mkaz/tmp/tmp)
    Finished test [unoptimized + debuginfo] target(s) in 0.17s
     Running target/debug/deps/tmp-4bcf431473cd6bf8

running 1 test
test test_add ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

Run a specific test using cargo test TESTNAME

For the example above, cargo test test_add